The present invention relates to a transmitting device for transmitting and receiving contents, such as audio visual materials, through networks which is suited to copy protects of the contents and to a content transmitting method.
In transmitting a material to be delivered, or content, between digital audiovisual devices, the device on the transmitting side implements a copy protect on the content for preventing it from being copied an unlimited number of times, by encrypting the content and sharing information for decryption with the content receiving side device so that the content cannot be correctly received and decrypted by other than the intended content receiving side device at the destination.
Among such copy protects employed by digital audiovisual devices is a method described in JP-A-2005-269288. The method proposed by JP-A-2005-269288 involves: classifying contents into categories of “Copy free (permitted to be copied without limitation)”, “Copy free with EPN asserted (permitted to be copied without limitation with an output protection)”, “Copy one generation (permitted to be copied for only one generation)”, “No more copies (no further copies permitted)” and “Copy never (no copies permitted)”; allowing the recording device to record only those contents categorized as “Copy free”, “Copy free with EPN asserted” and “Copy one generation” and requiring the recording device to, after making a copy, handle those contents in the “Copy one generation” category as being in the “No more copies” category; and requiring the device on the transmitting side to implement the encryption on all contents before transmitting them, except those in the “Copy free” category, thus preventing an uncontrolled copying of contents.
Further in JP-A-2005-269288 and JP-A-2007-36351, a technique is disclosed which, in a content transmission through a wired or wireless network, checks that the network is an in-house network so as to prevent copy-protected contents such as broadcast programs that have been recorded in house from being distributed unlimitedly to the outside the house.